The article by Daude R. et al: entitled “Head-Mounted Display als facharbeiterorientierte Unterstützungskomponente an CNC-Werkzeugmaschinen”, [“Head-Mounted Display as a component to assist skilled operators of CNC machine tools”], Werkstattstechnik, DE, Springer Verlag, Berlin, Vol. 86, No. 5, May 1, 1996, pp. 248-252, XP000585192 ISSN: 0340-4544, describes a head-mounted display (HMD) as a component to assist the skilled operator with the steps of setting up, feeding and trouble shooting in milling operations. The technical integration of the HMD into a modern NC control is explained, and the results of a laboratory trial of the HMD are mentioned.